During the post-WWII Nuremberg trials, the prevailing defence was, famously, “I was following orders.” As detailed in the documentary The Accountant of Auschwitz, the go-to then became, “I was just there. I didn’t kill anybody.”

Which is why the 2015 case of ex-Nazi SS officer Oskar Groning represented a change of course in addressing war crimes. Groning was, indeed, an accountant at the infamous Nazi death camp, one who catalogued the property of mostly Jewish detainees because, in his words, “they no longer needed it.”

But in a precedent set by the trial of the late Cleveland auto worker John Demjanjuk, German law was amended in 2009 to make it a crime simply to be at the scene of a war crime, in Groning’s case, simply to be an SS officer at Auschwitz.

To that extent, the law was akin to the U.S. RICO Act (Racketeer Influenced and Corrupt Organizations), which effectively made it a crime to belong to any organization that committed crimes, whether a Mafia family or a motorcycle gang.

So, was every German officer culpable at Auschwitz? Director Matthew Shoychet and writer/producer Ricki Gurwitz’s doc – which was the runner-up for most popular film at the recent Hot Docs festival – wrestles with that notion, and shines a light on an uncomfortable fact of post-War Germany.

To wit: Germany prosecuted relatively few of its accused war criminals. (Of 6,500 guards at Auschwitz, only 49 were ever prosecuted. We meet a U.S. war crimes investigator, Benjamin Ferencz, now in his 90s, who remains haunted by his inability to make prosecutions stick).

The irony is that Groning, who continued to maintain his own innocence until his death earlier this year, incriminated himself in the process of refuting the Holocaust deniers he detested. In 2005, he made numerous media appearances, including the BBC, confirming what he saw at the death camp, how the train passengers were separated, who went where and what happened to them.

As the only war crimes defendant to ever freely testify, Groning’s testimony in The Accountant of Auschwitz makes for morbidly fascinating viewing. Groning talks about his time there as “joyous.. gossiping and chatting, like a small town with a canteen and a cinema.” He is removed from the horrific events of the Holocaust, beyond being determined to confirm that they happened for history’s sake.

There are interviews with Groning’s neighbours in the German town of Luneberg who decry the prosecution of a nonagenarian – as indeed most of the still-living Nazi war criminals would be. If this new standard of culpability had been in place in the ‘40s, perhaps hundreds of thousands of Germans could have been charged. But now, it’s a mainly symbolic act, one that brings together in court surviving camp prisoners and their erstwhile captors – all in their dotage.

Still, these meetings make for dramatic scenes, to say the least, in The Accountant of Auschwitz. Many were there to express their undying hatred of Groning and the Auschwitz SS. But one survivor, Eva Moses Kor, created an uproar by forgiving Groning in court.

It’s a moment of intended grace that leaves many with a sour taste – symbolic of the conflicting emotions on display in what will be one of the last Nazi war crimes trials we ever witness.